Re: [Boost-Users] shared_ptr and make_indirect_iterator

From: Richard Wolf (richard_at_[hidden])
Date: 2002-08-28 18:04:24

----- Original Message -----
From: "Peter Dimov" <pdimov_at_[hidden]>
To: <Boost-Users_at_[hidden]>
Sent: Thursday, August 29, 2002 12:17 AM
Subject: Re: [Boost-Users] shared_ptr and make_indirect_iterator

> From: "Richard Wolf" <richard_at_[hidden]>
> > Hi
> >
> > I'm trying to use make_indirect_iterator on a container of shared_ptrs
as
> > follows:
> >
>
> [...]
>
> > int main()
> > {
> >     list<shared_ptr<A> > List2;
> >
> >      // This doesn't work
> >     for_each(make_indirect_iterator(List2.begin()),
> >                   make_indirect_iterator(List2.end()),
> >                   mem_fun_ref(&A::f));
> > }
>
> The reason is that make_indirect_iterator tries to instantiate
> std::iterator_traits< shared_ptr<A> >, and this fails, because
shared_ptr<A>
> is not an iterator.
>
> You can make the for_each work by using
>
> for_each(List2.begin(), List2.end(), boost::mem_fn(&A::f)); // in
> <boost/mem_fn.hpp>
>
> if that's what you want.
>

Thank you.  I suppose this means that the container must contain a type that
is an iterator rather than a pointer.  A raw pointer works because raw
pointers are iterators.  But....

The documentation of Indirect Iterator Adapter says :

"The indirect iterator adaptor augments an iterator by applying an extra
dereference inside of operator*(). For example, this iterator makes it
possible to view a container of pointers or smart-pointers (e.g.
std::list<boost::shared_ptr<foo> >) as if it were a container of the
pointed-to type."

Is the documentation incorrect, or have I misunderstood?

Thanks

Richard